1. Field of the Invention
This invention relates to an image data recording/reproducing method for recording original-image data representing an original image and reduced-image data representing a reduced image of the original image on a recording medium such as a memory card or magneto-optical disk, and for reading and outputting the reduced-image data from the recording medium on which the data has been recorded. The invention further relates to an image data recording apparatus and method as well as an image data reproducing apparatus, which are suited to the above-mentioned image data recording/reproducing method.
2. Description of the Prior Art
When original-image data representing an original image are recorded on a recording medium such as a memory card or magneto-optical disk, it has been contemplated to record reduced-image data representing a reduced image of the original image on the recording medium. If the recorded data are data representing a reduced image, the amount of image data is also small. As a result, quick readout is possible and the reduced image can be reproduced quickly as well. Reproducing the reduced image makes it possible to ascertain the content of the original image, which can be reproduced as necessary. The general practice is to generate the reduced-image data by subsampling the original-image data.
Since it is necessary to make the sizes of reduced images uniform, the quantity of reduced-image data is made uniform regardless of the coarseness or fineness of the original image and the quantity of original-image data. In order to make the quantity of reduced-image data uniform, consideration has been given to changing the subsampling ratio in dependence upon the quantity of original-image data. However, when the subsampling ratio is changed image by image in dependence upon the quantity of original-image data for the purpose of uniformalizing the quantity of reduced-image data, the smaller the quantity of original-image data, the larger the ratio of the quantity of reduced-image data to the quantity of original-image data. Accordingly, the quantity of original-image data capable of being recorded diminishes as a result of recording the reduced-image data. For example, consider a case where original-image data are recorded on a recording medium upon being subjected to data compression at a compression ratio of 1/8. If the size of a reduced image is 80 pixels horizontally and 64 pixels vertically, then the quantity of reduced-image data will be five kilobytes. In this case, for original-image data representing an original image having 1280 pixels horizontally and 1024 pixels vertically, the quantity of data recorded on the recording medium will be 160 kilobytes. For original-image data representing an original image having 640 pixels horizontally and 512 pixels vertically, the quantity of data recorded on the recording medium will be 41 kilobytes.
Regardless of the quantity of original-image data to be recorded on the recording medium, the quantity of reduced-image data is fixed. The smaller the quantity of original-image data, the more the difference between the quantity of original-image data and the quantity of reduced-image data diminishes and the smaller the advantage of recording the reduced-image data on the recording medium together with the original-image data becomes. These problems become particularly conspicuous if the recording medium is one having a small recording capacity.
Furthermore, if the area for recording the reduced-image data on the recording medium is not decided in advance, all recording areas must be searched when a reduced image is to be reproduced. As a result, reduced images cannot be reproduced in rapid fashion.